Authors/Thomas Aquinas/posteriorum/L2/Lect15

Lecture 15 Two errors are excluded. What is really required for constituting a definition according to the method of division?

Latin	English
	Lecture 15 (97a6-b6) TWO ERRORS ARE EXCLUDED.-WHAT IS REALLY REQUIRED FOR CONSTITUTING A DEFINITION ACCORDING TO THE METHOD OF DIVISION?
lib. 2 l. 15 n. 1 Postquam philosophus ostendit veritatem circa divisionem generis, quae assumitur ad definiendum, hic excludit duos errores. Secundum, ibi: omne autem incidere et cetera. Circa primum tria facit. Primo proponit exclusionem erroris: et dicit quod non est necessarium quod ille qui dividendo definit, sciat omnia quae sunt in mundo.	After presenting the truth concerning the division of the genus which is used in defining, the Philosopher here excludes two errors. In regard to the first one he does three things: First (97a6) he excludes the error and says that it is not necessary that one who defines by dividing should know all the things which exist in the world.
lib. 2 l. 15 n. 2 Secundo, ibi: et tamen impossibile quidam dicunt etc., narrat opinionem errantium. Dicebant enim quidam, quod non potest cognosci differentia alicuius ad omnia alia entia, nisi omnia alia entia cognoscantur, ut patet in aliquibus duobus, quorum differentiam cognoscere non possumus nisi utrumque cognoscamus. Addebant autem quod non est possibile quod aliquid sciatur quid est, nisi cognoscatur differentia eius ad omnia alia. Id enim a quo aliquid non differt est idem ei: illud autem a quo differt est alterum ab ipso. Non autem possumus scire quid sit unumquodque, nisi sciamus quid sit idem ei, et quid alterum ab eo. Et secundum hoc concludebant quod non potest aliquid cognosci nisi omnia cognoscantur.	Secondly (97a7) he sets forth the opinion of those who make this error. For some have said that it is not possible to know the difference between one thing and everything else, unless everything else is known, as is plain in regard to any two given things, whose difference we cannot know unless we know both things. However, they added that the quid est of something cannot be known, unless the difference between it and everything else is known. For that wherein something is not different is identical with it, whereas that by which something differs is other than it. But we cannot know what a thing is, unless we know what is the same as it and what is other than it. According to this, therefore, they concluded that something cannot be known unless everything is known.
lib. 2 l. 15 n. 3 Tertio, ibi: primum quidem igitur etc., improbat quod dictum est dupliciter. Et primo quidem interimit hoc quod dictum est, quod illud a quo aliquid differt, est alterum. Loquimur enim nunc de eodem et de altero secundum essentiam, quam significat definitio. Manifestum est autem quod etiam in eadem specie sunt multae differentiae accidentales, quae non diversificant substantiam speciei, quam significat definitio, nec per se insunt. Unde consequens est quod non omnis differentia facit talem alteritatem, quam necessarium sit cognoscere ad definiendum.	Thirdly (97a11) he disproves what they say in two ways. First, he destroys the statement according to which it is said that that by which something differs is something other. For we are now speaking about what is the same and what is other according to the essence which the definition signifies. But it is obvious that even in the same species there are many accidental differences which neither diversify the substance of the species which the definition signifies, nor are in it per se. Hence it follows that not every difference makes something other in such a way that it must be known if one is to define.
lib. 2 l. 15 n. 4 Secundo, ibi: postea cum accipiat opposita etc., improbat quae dicta sunt alio modo. Cum enim ille qui vult definire dividendo, accipiat oppositas differentias hoc modo, quod omne quod continetur sub diviso, cadat sub hoc membro divisionis vel sub illo, et accipiat sub altero membrorum illud cuius definitio quaeritur, si hoc quod intendit definire, cognoscat sub illo membro divisionis contineri; non differt ad propositum utrum sciat vel nesciat de quibuscunque aliis rebus praedicentur oppositae differentiae. Puta si dividam animal per rationale et irrationale, et accipiam propositum sic hominem contineri sub rationali, non requiritur quod sciam de quibus irrationale praedicetur, nec qualiter illa ad invicem differant. Manifestum est enim quod si aliquis sic procedat, scilicet dividendo genus per primas differentias eius, et accipiendo propositum sub altero membro, dividens quousque perveniatur in illa quae ulterius dividi non possunt essentialibus differentiis; sic procedens habebit definitionem substantiae, quam quaerebat.	Secondly (97a13), he disproves it another way. For since one who proposes to define by dividing must take opposing differences in such a way that everything contained under the divided whole falls under this member or that member of the division, and must subsume under one or the other of the members that whose definition is sought (if he knows that the thing he intends to define is contained under that member of the division), then it makes no difference, so far as his intent is concerned, whether he knows or does not know the things of which the opposing differences might be predicated. For example, if I divide animal into rational and irrational, and assume that man is contained under animal in the way we have proposed, it is not required that I know the things of which irrational is predicated or how they differ from one another. For it is obvious that if someone proceeds in this way, namely, by dividing the genus into its first differences and taking the definitum [thing being defined] as subsumed under one of the members and then dividing until certain items are reached that cannot be further divided by essential differences, then by proceeding in this manner he will have the definition of the substance which he was seeking.
Decipiebantur ergo praedicti homines ex eo quod non distinguebant inter cognoscere aliquid in communi et in speciali. Oportet enim quod quicunque scit quid est aliquid, cognoscat omnia alia in communi, non autem in speciali. Puta qui scit quid est homo, oportet quod sciat hominem per hoc quod est animal, distingui ab omnibus quae non sunt animalia; et per hoc quod est rationale, distingui ab omnibus quae non sunt rationalia. Non enim oportet quod illa cognoscat, nisi secundum hoc commune quod est non animal, vel irrationale.	Therefore, the persons mentioned above were deluded for failing to distinguish between something in common and in detail. For it is required of one who knows what something is, that he know all things in common but not in detail. For example, one who knows what man is must know that it is through being an animal that man is distinguished from all things that are not animals, and through being rational that man is distinguished from all things that are not rational. But it is not required that he know anything more about these others than is included in the general notion of non-animal or irrational.
lib. 2 l. 15 n. 5 Deinde cum dicit: omne autem incidere etc., excludit secundum errorem. Posset enim aliquis credere quod quicunque utitur divisione ad definiendum, indigeat petere quod totum divisum contineatur sub membris divisionis; sed ipse dicit quod hoc non est necessarium, si opposita, per quae fit divisio, sint immediata; quia secundum hoc necessarium est quod totum divisum sub altero oppositorum contineatur, dum tamen accipiantur primae differentiae alicuius generis. Differentiae enim quae sunt immediatae si comparentur ad genus inferius, non sunt immediatae si comparentur ad genus superius. Sicut par et impar sunt immediata si comparentur ad numerum, cuius sunt propriae differentiae; non autem si comparentur ad quantitatem.	Then (97a19) he excludes the second error. For someone might believe that whoever uses division for defining must assume that the entire whole is contained under the members of the division. But he says that this is not necessary, if the opposites through which the division is made are immediate; because the divided whole is necessarily contained under one of the opposites, provided the first differences of the genus were taken. For differences which are immediate when compared to a lower genus are not immediate if compared to a higher genus. For example, even and odd are immediate if compared to number of which they are proper differences, but not if they are compared to quantity.
lib. 2 l. 15 n. 6 Deinde cum dicit: ad construendum autem terminum etc., postquam exclusit ea quae non requiruntur ad divisiones definiti, hic ostendit quae secundum rei veritatem requirantur. Et primo, proponit quod intendit; secundo, manifestat propositum; ibi: est autem horum unum. Dicit ergo primo quod ad hoc quod aliquis constituat terminum, idest definitionem, per viam divisionis, tria oportet considerare: quorum primum est, ut ea quae accipiuntur, praedicentur in eo quod quid est; secundum est, ut ordinetur quid sit primum et quid secundum; tertium est, quod accipiantur omnia quae pertinent ad quod quid est, et nihil eorum praetermittatur.	Then (97a23), after rejecting things which are not required in the divisions of the definitum, he shows what is really required. First, he proposes what he intends. Secondly, he manifests his proposal (97a25). He says therefore first (97a23) that in order to achieve a term, i.e., a, definition, by the method of division three things must be observed: first, that the things which are taken be predicated in quod quid; secondly, that they be arranged according to what is first and what is second; thirdly, that everything taken pertain to the quod quid and that nothing be omitted.
lib. 2 l. 15 n. 7 Deinde cum dicit: est autem horum unum etc., manifestat propositum. Et primo, ostendit quomodo tria praedicta possunt observari; secundo, ostendit quod praedicta tria observata sufficiant; ibi: manifestum est autem et cetera. Circa primum tria facit. Primo ostendit quomodo observetur primum: et dicit quod unum horum (scilicet quod accipiantur ea quae praedicantur in eo quod quid est) observatur, primo quidem per hoc quod homo potest inducere syllogismos quod id quod assumitur insit, sicut cum disputatur ad problema de accidente; secundo, ut ostendatur quod praedicatur in eo quod quid, per ea quibus disputatur ad problema de genere.	Then (97a25) he manifests his proposal. First, he shows how these three rules can be observed. Secondly, he shows that it is enough to observe those three rules (97b1). In regard to the first point he does three things. First (97a25), he shows how the first rule is observed, saying that this one (namely, that one take things which are predicated in quod quid) is observed, first of all, by the fact that a person can form syllogisms to show that what is assumed is in the thing (as is done when there is dispute about whether something is an accident); secondly, to show that it is predicated in quod quid (as is done when there is dispute about a genus).
lib. 2 l. 15 n. 8 Secundo, ibi: ordinare autem sicut oportet etc., manifestat quomodo observetur secundum, scilicet debita ordinatio partium; et dicit quod tunc ordinantur partes definitionis sicut oportet, si aliquis primo accipiat id quod est primum; et hoc erit si aliquis primo accipiat id quod consequitur ad alia posterius accepta, et non e converso. Hoc enim est communius et prius. Necesse est autem aliquid huiusmodi accipi in definitione tanquam genus, puta cum dicitur quod homo est animal gressibile bipes. Si enim est gressibile bipes, est animal, sed non e converso. Cum ergo iam acceperimus animal tanquam primum, idem modus observandus est in ordinatione inferiorum. Accipietur enim quasi secundum in definitione illud quod secundum rationem praemissam erit primum inter omnia sequentia; et similiter accipietur tertium id quod est primum respectu habitorum, idest consequentium. Semper enim, remoto superiori, illud quod est habitum, idest immediate consequens, erit primum omnium aliorum. Et ita est etiam in omnibus aliis, puta in quarto et in quinto, si tot oporteat partes definitionis esse.	Secondly (97a28), he shows how the second rule is observed, namely, that there be a correct ordering of the parts. And he says that the parts of a definition are arranged as they should, if one takes what is first—and he will do this, if he first takes that which is implied by the other things that are taken later, and not conversely. For this is more common and prior. But such a thing must be taken in the definition as a genus, as when it is stated that man is an animal, two-legged and walking. For if he is a two-legged walker, he is an animal; but not vice versa. Therefore, when I have taken animal as first, the same method must be observed in arranging the other items. For the second item to be employed in the definition will be that which according to the foregoing description will be first among all the others; likewise, the third item to be taken will be that which is first in respect of the items had, i.e., following. For it will always turn out that when the more general item has been removed, that which is had, i.e., that which immediately follows, will be true in regard to all the other items, say a fourth and a fifth, if that many parts are needed for the definition.
lib. 2 l. 15 n. 9 Tertio, ibi: quod autem haec omnia sint etc., manifestat, qualiter possit tertium observari. Et dicit quod manifestum erit omnia quae pertinent ad quod quid est accipi in definitione secundum modum supra dictum, ex hoc scilicet quod dividendo aliquod genus accipimus primas eius differentias, sub quibus divisum universaliter continetur; sicut quod omne animal est hoc vel illud, puta rationale vel irrationale, et accipimus quod illud quod intendimus definire, est hoc, puta rationale. Et iterum accipiemus hoc totum, scilicet animal rationale, et dividemus ipsum per differentias proprias; sed quando iam devenerimus ad ultimam differentiam, iam non erit dividere per alias differentias specificas: sed statim ultima differentia addita, hoc, cuius definitio quaeritur, in nullo differet specie a simul toto, idest a ratione congregata ab omnibus partibus acceptis; sicut homo non differet specie ab aliquo eorum de quibus praedicatur animal rationale mortale.	Thirdly (9704), he shows how the third rule can be observed. And he says that it will be obvious that all items pertaining to the quod quid are present in the definition according to the aforesaid method, because when we divide the genus, we take its first differences, under which the divisum is universally contained; for example, that every animal is this or that, i.e., rational or irrational, and we assume that what we intend to define is this, i.e., rational. And again we take this whole, namely, rational animal, and divide it by its proper differences; but when we arrive at the ultimate difference, it will be impossible to divide by other specific differences, but as soon as the ultimate difference is added, the thing whose definition is being sought will differ in no way from the assembled whole, i.e., from the description formed by all the parts that were taken. Thus, man does not differ specifically from any of those of whom rational mortal animal is predicated.
lib. 2 l. 15 n. 10 Deinde cum dicit: manifestum enim est etc., ostendit quod tria praedicta observata sufficiant ad definiendum, quia definitio neque superfluum neque diminutum habebit. Quod autem non apponatur aliquid plus quam debeat, manifestum est per primum trium praedictorum; quia scilicet accepta sunt solum ea quae praedicantur in eo quod quid et talia necesse erat accipere. Similiter etiam manifestum est quod nihil deficit. Aut enim deficeret genus, aut differentia. Sed quod genus non deficiat, patet ex secundo trium praedictorum. Acceptum est enim primum id sine quo non sunt alia, et quod potest esse sine aliis, et hoc est genus. Et cum genere postea acceptae sunt differentiae. Sed quod differentiae omnes sint acceptae, patet per tertium praedictorum trium; quia non amplius potest accipi posterior differentia post illam cuius diximus non esse aliam differentiam; quia iam sequeretur quod ultimum acceptum adhuc differret differentia essentiali, cum tamen dictum sit, quod non differat.	Then (97b1) he shows that the observance of the three aforesaid rules is sufficient for defining, because the definition will have neither more nor less than it should. That no more has been assigned than it should have is obvious from the first rule, namely, because the only things accepted are items predicated in quod quid; and it was necessary to accept such things. Likewise it will be clear that nothing has been omitted. For either the genus or the difference might be missing. But that the genus is not missing is clear from the second rule; for the first thing taken was the item without which the others do not exist, and which can exist without the others: and this is the genus. And with the genus the differences were then taken. But that all the differences have been taken is obvious from the third rule, since there can be no further subsequent difference taken after the one concerning which we have said that it has no difference; otherwise it would follow that what had been admitted to be the last would still differ with an essential difference, whereas it had been said that it does not have a difference.
Similiter etiam ex praemissis patet quod non intermittatur aliqua differentia in medio, per hoc scilicet quod semper accipiuntur primae differentiae. Unde relinquitur quod sufficiat tria praedicta ad definiendum observari.	Similarly, it is obvious from the foregoing that no difference has been left out in the meantime, namely, because first differences are always taken. Hence it remains that for defining it is sufficient that the three aforesaid rules be observed.